<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<style>
			div#box{
				text-align: center;
			}
			
			div#box div#btn {
				margin: auto;
				width: 50px;
				height: 50px;
				line-height: 50px;
				background-color: #ddd;
				border-radius: 100%;
				color: #fff;
				cursor: pointer;
			}
		</style>
	</head>
	<body>
		<div id="box">
			<div id="btn">
				开
			</div>
			<img src="img/灭灯.gif"/>
		</div>
		<script>
			(function(){
				var btn = document.querySelector("#btn");
				var img = document.querySelector("#img");
				btn.onclick = function(){
					console.log("this:",this);
					if(this.innerHTML == "开"){
						img.src = "img/亮灯.gif";
						this.innerHTML = "关";
						this.style.backgroundColor = "green";
					} else {
						img.src = "img/灭灯.gif";
						this.innerHTML = "开";
						this.style.backgroundColor = "#ddd";
					}
				}
			}())
		</script>
	</body>
</html>
